Kevin, Thanks for the reply but the transfer case is not switching positions. It is in 4H and won't switch to 2H or 4L and I have no light. Its not that the hubs are not locking. I can go thru the snow, it is in 4H.

 

dmodracer3, where is the 4X4 module? My repair manual on CD doesn't mention a 4X4 module. I did change the relays.

 

its mounted right on the passenger side front fender right next to the battery.

 

The vacuum system has NOTHING to do with the light on the dash. If the light on the dash is not coming on, the transfer case is not shifting.

 

well after reading some of the forums im still stumped,but i will change the two relay fuse's in the black box and maybe with some luck the relay on the passenger side will work as there is no power to it ,but one question is there something behind the radio as far as fuse's for on the fly switch

 

Bumping up this thread because I'm having a similar issue. Yesterday I used 4WD a few times, and the last time I tried I heard a little clunk and the 4WD light wouldn't come on anymore. I went under the truck and tested for power at the shift motor on the T-case. No power. So where would you guys go from here? Which fuse should I be testing? Relay? Switch? I don't have a FSM yet, since I just bought the truck recently, so any help on troubleshooting methods is much appreciated.

 

Add:

I just went out to the truck and tried to put it in 4WD again. When I first turn the ignition on (not the engine), I select 4HIGH and I can hear the shift motor trying to engage the t-case. It'll hum for a second, then go silent for a second, then hum for a second, and go off for a second. If I put it in 4LOW or 2HIGH the motor stops, and subsequent attempts to engage 4HIGH result in no motor noise at all. If I turn the truck off completely and try again later, the same thing will happen.

At this point I'm pretty confused. Do I have a problem with a relay (sporadic shift motor activity), as well as a mechanical problem inside the T-case (shift motor humming but 4WD light not coming on, indicating that the motor is trying to engage, but something in the t-case is not engaging)?

Thanks for any help!

 

BTW, truck is a 1999 F-250 SD PS 7.3

 

Turn your ignition to ON and do not crank it. Turn your heater on with the vents going to the floor. Then turn your 4x4 switch to 4WD High. See if your air then defaults to blowing out of your defrost vents. If so, then you have a vacuum leak in your system.

I just reread your post where you stated your 4x4 light is NOT coming on your dash. This may be a different issue and not a vacuum leak.

 

This is slightly unrelated, but in my 99 super duty i replaced the stock automatic locking hubs for manual warn hubs as they where half the price and it never bothered me to have to lock them in. I didn't know how hard it would be to also switch to a floor shifter for the transfer case.

 

It looks like it might be a good idea to get a scan tool as per this:

https://www.motorcraftservice.com/pu...21/SXOMAIN.HTM

Which scan software do you guys like best for these trucks?

 

That's a neat site. Can you post a similar link for a 2003 F250 7.3 SD?

 

I got it from the tech folder

 

https://www.ford-trucks.com/forums/7...ml#post6739272

 

Thanks. Looks like 2002 is the highest manual I can access.